CHAPTER TWO: LITERATURE REVIEW

In document CHAPTER TWO: LITERATURE REVIEW (halaman 41-49)

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18 2.1 Diabetes mellitus

2.1.1 Definition of diabetes mellitus

Diabetes mellitus (DM) is a common chronic disease characterized by hyperglycemia and other metabolic abnormalities and is mostly due to insulin deficiency, insulin resistance and/or increased hepatic production of glucose (in type 2 diabetes). Diabetes is “a group of metabolic diseases characterized by hyperglycemia and resulting from a defect in insulin secretion, insulin action or both” (American Diabetes Association, 2005). DM occurs when the body fails to absorb glucose due to factors associated with insulin availability or inappropriate insulin action.

2.1.2 Types of diabetes

Genetically, etiologically, and clinically, diabetes is a heterogeneous group of disorders (Koda-Kimble et al., 2009). Based on the etiology of diabetes, there are three main types of diabetes: type 1, type 2 and gestational diabetes. However, other specific types of diabetes also exists such as maturity onset diabetes of the young (MODY) in which these forms of diabetes are frequently characterized by onset of hyperglycemia at an early age (generally before age 25 years) and are characterized by impaired insulin secretion with minimal or no defects in insulin action (American Diabetes Association, 2011; The Expert Committee on the Diagnosis Classification of Diabetes Mellitus, 2007). Moreover, latent autoimmune diabetes in adults (LADA), is a subgroup of type 2 diabetes and the patients share many genetic and immunological similarities with type 1 diabetes, suggesting that LADA, like type 1 diabetes, is an autoimmune disease (Naik et al., 2009).

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Type 1 diabetes occurs when the insulin-producing cells in pancreas (beta cells) are damaged or destroyed by an autoimmune process resulting in a reduced or impeded insulin production (Atkinson and Maclaren, 1994; Falorni et al., 1995). The exact etiology of type 1 diabetes is not known, but it is believed that a patient’s genetic background in the context of a possible infectious trigger leads to the development of the disease (Genuth et al., 2003a; Mayfield, 1998). Type 1 diabetes mostly afflicts individuals around the time of puberty and is treated by insulin, diet and exercise (Franz et al., 2004; Koda-Kimble et al., 2009).

Type 2 diabetes is the most common type of diabetes, occurring in about 90% of diabetic patients. Type 2 diabetes results when the body produces less insulin or when the cells of the body become insensitive to insulin (American Diabetes Association Website). While the incidence of type 1 diabetes is highest in children and around puberty, type 2 diabetes also known as adult onset diabetes (Howlett and Lillie, 2006). However, the incidence of type 2 diabetes in children is also increasing along with the epidemic of childhood obesity (Ludwig and Ebbeling, 2001;

Silverstein and Rosenbloom, 2001). Type 2 diabetes has been found to have a strong genetic component with a three-fold higher risk among the siblings of an individual with diabetes (Elbein, 2002).

Gestational diabetes, which is the third main type of diabetes, occurs in about 4% of pregnant women in the US (Engelgau et al., 1995). Like type 1 diabetes, the exact etiology is not well understood, but hormones from the placenta are believed to block the action of insulin in the mother’s body (Koda-Kimble et al., 2009). Usually, gestational diabetes is temporary and disappears after the end of the pregnancy;

however, an increased risk of impaired glucose tolerance and type 2 diabetes remains and women with gestational diabetes have a 17%-63% risk of developing type 2

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diabetes within the next 5-16 years (Ben-Haroush et al., 2004; Hanna and Peters, 2002; Henry and Beischer, 1991).

The fourth type of diabetes, which is secondary to other conditions, consists of diabetes associated with a genetic defect in the function of the beta cells of the pancreas, a genetic defect in the action of insulin, diseases of the pancreas, other genetic syndromes, drug use or chemical exposure (Diabetes Mellitus Information, 2006).

The assessment and discussion in this study is limited to type 2 DM and the term diabetes that subsequently appears in this study refers to type 2 DM.

2.1.3 Diagnosis of diabetes

Diabetes is usually diagnosed when one or more of the usual signs and symptoms of diabetes are present and confirmed by a high level of glucose in a venous blood sample. The recommended criteria for the diagnosis of DM are as follows (American Diabetes Association, 2009; International Diabetes Federation, 2005; Ministry of Health Malaysia, 2009; Rodbard et al., 2007).

1- When there are symptoms of diabetes (polyuria, polydipsia and weight loss) associated with causal (any time of day, with no regard to the last meal) fasting blood sugar (FBS) more than 11.1 mmol/L

2- FBS is equal to or more than 7 mmol/L

3- Two hour postprandial plasma glucose is equal to or more than 11.1mmol/L.

21 2.1.4 Clinical presentation of type 2 diabetes

Type 2 diabetes is typically diagnosed incidentally during a routine physical examination or when the patient seeks attention for another complaint. This is because symptoms are so mild and their onset so gradual that they can easily be explained away (Koda-Kimble et al., 2009). However, when the patients giving a history of their illness, fatigue, polyuria, and polydipsia are acknowledged (Alberti and Zimmet, 1998; Boron and Boulpaep, 2003; Ganong and Systems, 1995; Koda-Kimble et al., 2009). Weight loss is uncommon, and macrovascular disease is also often evident at diagnosis while the presence of microvascular complications at diagnosis suggests the presence of undiagnosed or subclinical diabetes for 7 to 10 years (Koda-Kimble et al., 2009).

2.1.5 Glycosylated hemoglobin A1C (HbA1C)

HbA1C is a result of the reaction between glucose and hemoglobin in the blood. The hemoglobin is exposed to glucose in the blood and when there is a higher level of glucose, more HbA1C will be formed. HbA1C is an important marker and is an index for glycemic control. HbA1C is considered as the gold standard for the evaluation of diabetes control as it provides an average blood glucose over the preceding two to three months (American Diabetes Association, 2009; Katsilambros and Tentolouris, 2003). The normal level of HbA1C in a non-diabetic person ranges from 3.8-6.4% of the total hemoglobin (Goldstein et al., 2004; Kasper et al., 2005).

According to the 2009 American Diabetes Association recommendations, a HbA1C less than 7% is desired for good glycemic control (American Diabetes Association,

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2009), while a HbA1C equal to or less than 6.5% was recommended by the American Association of Clinical Endocrinologists (Rodbard et al., 2007).

The target level of equal or less than 6.5% HbA1C for patients with type 2 diabetes is recommended by the Malaysian Clinical Practice Guidelines for the management of type 2 diabetes (Ministry of Health Malaysia, 2009). There is strong evidence that HbA1C should be measured routinely in all patients with diabetes (type 1 and 2) in order to evaluate the degree of glycemic control. Glycemic goal should be based on the results of prospective randomized clinical trials like the Diabetes Control and Complications Trial (DCCT), the United Kingdom Prospective Diabetes Study (UKPDS) and Action in Diabetes and Vascular disease: preterAx and diamicroN Controlled Evaluation (ADVANCE) or based on the guidelines for the management of diabetes (Sacks et al., 2002).

2.1.6 Diabetes complications

There are different forms and types of complications associated with diabetes which vary from acute to chronic in onset and can be classified by the type of tissues or cells where complications occur (Fowler, 2008). Generally, complications are more common in patients who have difficulty in controlling their blood glucose at acceptable levels (Stratton et al., 2000).

23 2.1.6.1 Acute complications of diabetes

Primary or secondary hypoglycemia is an acute complication of diabetes, which can be severe and sometimes have rapid consequences and multiple causes, depending on the etiology and especially the presence or absence of hyperinsulinemia (Bibergeil, 1988). Diabetic ketoacidosis also is an acute metabolic complication of diabetes resulting primarily from intense insulin deficiency that mostly occurs with type 1 diabetes and occasionally in type 2 diabetes and which is associated with a mortality rate of 10% (Walker et al., 1989). Hyperosmolar non-ketogenic coma results from profound dehydration as a result of fluid loss (pneumonia, burns, stroke or a recent operation) or inadequate fluid intake. It is associated with a greater than 50%

mortality rate and is considered a true medical emergency (Walker et al., 1989).

2.1.6.2 Chronic complications of diabetes

The long term complications associated with diabetes can develop in patients with type 2 diabetes which include micro and macro-vascular complications. Macro-vascular complications are responsible for stenosis at the three major arteries which are the coronary, cranial and limb arteries (Nesto, 1988; Pyorala and Laakso, 1983).

Micro-vascular complications of diabetes affect the small blood vessels and capillaries resulting in thickening of the basement membrane of the capillaries throughout the body. Among the problems caused by this complications are retinopathy, nephropathy and neuropathy (Cheung and Wong, 2008; King and Brownlee, 1996). Diabetic neuropathy is classified into different types of diabetes complications, in which patients suffer from numbness or irritation at the tips of the limbs with wasting of manual muscles and impaired reflexes. Neuropathy is the most common complication and occurs in 12% of patients at the time of diagnosis and in

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25% of patients after 25 years of diabetes (Vinik et al., 2000). Other chronic complications of diabetes includes autonomic neuropathy, diabetic foot disorder, carpal tunnel syndrome, increased susceptibility to infection, poor circulation and poor renal function (Herfindal and Gourley, 2000).

2.1.7 Diabetes management

Diabetes management normally follows the clinical diagnosis with lifestyle modification, pharmacotherapy and patient education to encourage self-care and to achieve glycemic control (Funnell et al., 2009; Funnell et al., 2007; Martin et al., 2005). This involves, in addition to the primary medical evaluation of patients, a variety of strategies to provide adequate education to the patients and considers diabetes self-management education as an integral part of diabetes management with dietary planning, pharmacotherapy and exercise (American Diabetes Association, 2009; Rodbard et al., 2007). For proper implementation of self-management in therapeutic plans, a combination of behavioral strategies to improve self-management requires a multidisciplinary team effort from physicians, pharmacists and nurses (American Diabetes Association, 2009). Teaching self-management is time consuming and requires repeated contact with health care professionals for education, self-monitoring and the assessment of progress. The approach to patients should be individualized, taking into consideration their culture, economic situation, knowledge and beliefs regarding the disease and treatment, response to medication and changes in status over time.

The aim of adequate diabetes management is to reduce the acute and chronic complications of diabetes, principally by maintaining good glycemic control and

In document CHAPTER TWO: LITERATURE REVIEW (halaman 41-49)